“Interesting, isn’t it?” she says. “You’d never think of saying to a blind person, ‘Slow down and you’ll be able see,’ or ‘If you just tried a little harder you could see.’ But most of us think if a stutterer just relaxed and tried a little harder, he could speak fluently. That’s not the case,” says Montgomery, M.S., CCC-SLP, executive director and founder of The American Institute for Stuttering in New York City, N.Y.

Stuttering is a chronic dysfluency or break in fluent speech. It’s characterized by sound, syllable, word or phrase repetitions; hesitations, fillers (um, ah) and revisions in word choices. It can also include unnatural stretching out of sounds and blocks in which a sound gets stuck and just won’t come out. Stuttering may be accompanied by muscle tension, facial tics and grimaces.

No one really knows for sure exactly what causes it, but researchers believe there’s a neurological basis with a strong genetic component. Currently, the medical community categorizes stuttering as a psychiatric disorder — just like they do schizophrenia and bipolar disorder.

“There are probably multiple factors that can cause stuttering,” says Gerald Maguire, M.D., assistant clinical professor and director of residency training in the department of psychiatry at the University of California at Irvine. “There is a strong genetic component — stuttering does run in families. But it may be a combination of genetics, something neurological and something environmental. Since about 99 percent of all stutterers develop the disorder in childhood — usually before age 9 or 10 — it indicates that something occurs in the developing brain.”

“The idea that stuttering is a brain disorder in the same category as schizophrenia and bipolar disorder is very controversial,” says Maguire, a stutterer. In fact, there has been a push to recategorize stuttering as something other than psychiatric. “Some feel it attaches a stigma to a disorder that’s already very misunderstood by most,” Maguire said.

Among the things researchers do know about stuttering is that it’s not caused by emotional or psychological problems. It’s not a sign of low intelligence. The average stutterer’s IQ is 14 points higher than the national average. And it’s not a nervous disorder or a condition caused by stress. “If stress caused stuttering, we’d all be stutterers,” says Montgomery. Stuttering can, however, be made worse by anxiety or stress. And anxiety and stress can be a product of stuttering.